Genetically targeted radiotherapy for multiple myeloma

Vaccinia virus and peptide-receptor radiotherapy synergize to improve treatment of peritoneal carcinomatosis

Tumor-specific overexpression of receptors enables a variety of targeted cancer therapies, exemplified by peptide-receptor radiotherapy (PRRT) for somatostatin receptor (SSTR)-positive neuroendocrine tumors. While effective, PRRT is restricted to tumors with SSTR overexpression. To overcome this limitation, we propose using oncolytic vaccinia virus (vvDD)-mediated receptor gene transfer to permit molecular imaging and PRRT in tumors without endogenous SSTR overexpression, a strategy termed radiovirotherapy. We hypothesized that vvDD-SSTR combined with a radiolabeled somatostatin analog could be deployed as radiovirotherapy in a colorectal cancer peritoneal carcinomatosis model, producing tumor-specific radiopeptide accumulation. Following vvDD-SSTR and ¹⁷⁷Lu-DOTATOC treatment, viral replication and cytotoxicity, as well as biodistribution, tumor uptake, and survival, were evaluated. Radiovirotherapy did not alter virus replication or biodistribution, but synergistically improved vvDD-SSTR-induced cell killing in a receptor-dependent manner and significantly increased the tumor-specific accumulation and tumor-to-blood ratio of ¹⁷⁷Lu-DOTATOC, making tumors imageable by microSPECT/CT and causing no significant toxicity. ¹⁷⁷Lu-DOTATOC significantly improved survival over virus alone when combined with vvDD-SSTR but not control virus. We have therefore demonstrated that vvDD-SSTR can convert receptor-negative tumors into receptor-positive tumors and facilitate molecular imaging and PRRT using radiolabeled somatostatin analogs. Radiovirotherapy represents a promising treatment strategy with potential applications in a wide range of cancers.

Stable HIV decoy receptor expression after in vivo HSC transduction in mice and NHPs: Safety and efficacy in protection from SHIV

We aim to develop an in vivo hematopoietic stem cell (HSC) gene therapy approach for persistent control/protection of HIV-1 infection based on the stable expression of a secreted decoy protein for HIV receptors CD4 and CCR5 (eCD4-Ig) from blood cells. HSCs in mice and a rhesus macaque were mobilized from the bone marrow and transduced by an intravenous injection of HSC-tropic, integrating HDAd5/35++ vectors expressing rhesus eCD4-Ig. In vivo HSC transduction/selection resulted in stable serum eCD4-Ig levels of ∼100 μg/mL (mice) and >20 μg/mL (rhesus) with half maximal inhibitory concentrations (IC50s) of 1 μg/mL measured by an HIV neutralization assay. After simian-human-immunodeficiency virus D (SHIV.D) challenge of rhesus macaques injected with HDAd-eCD4-Ig or a control HDAd5/35++ vector, peak plasma viral load levels were ∼50-fold lower in the eCD4-Ig-expressing animal. Furthermore, the viral load was lower in tissues with the highest eCD4-Ig expression, specifically the spleen and lymph nodes. SHIV.D challenge triggered a selective expansion of transduced CD4+CCR5+ cells, thereby increasing serum eCD4-Ig levels. The latter, however, broke immune tolerance and triggered anti-eCD4-Ig antibody responses, which could have contributed to the inability to eliminate SHIV.D. Our data will guide us in the improvement of the in vivo approach. Clearly, our conclusions need to be validated in larger animal cohorts.

Theragnostics before we found its name

Theragnostics embraces "gnosis" and "prognosis" and concerns a treatment strategy which combines diagnostics with therapeutics. The birth of what we call today theragnostics can be traced in 1936, with the proposal of radioiodine, the first radiopharmaceutical approved in 1951 by FDA, in USA, as 131I sodium iodide. In 1957, 89Sr was also approved as first therapeutic radiotracer for skeletal metastases, followed in the subsequent years by 186Rh, 153Sm and, more recently, 223Ra, the first alpha emitter clinically utilized, allowing curative results and not only a palliative effect. Proposed in first eighties as [131I] Metaiodobenzylguanidine (MIBG), the theragnostic couple 123I/131I MIBG is still used in neural crest tumors, while, starting from partially unsatisfactory results in 70's, models based on antibodies for radioimmunoscintigraphy/radioimmunotherapy have been subsequently upgraded thanks to the introduction of monoclonal antibodies and other significant biological and technical improvements. The "Theragnostics called with this name" can be dated to early 90's with the first proposal of the somatostatin model, actually widely operating in neuroendocrine tumors with radio-chelates usable for diagnosis and therapy. Since then, many investigators are working on new theragnostics agents, also outside of the nuclear medicine, based on peptides, antibodies and other tools to find new models applicable in the clinical practice. The fast growth is stimulated by the interest of big pharma. Theragnostic concepts are the roots of nuclear medicine and new great goals are soon to be achieved in the direction of an increasing precision and tailored medicine.

Quantitative imaging and dynamics of tumor therapy with viruses

Cancer therapy remains challenging due to the myriad presentations of the disease and the vast genetic diversity of tumors that continuously evolve and often become resistant to therapy. Viruses can be engineered to specifically infect, replicate, and kill tumor cells (tumor virotherapy). Moreover, the viruses can be "armed" with therapeutic genes to enhance their oncolytic effect. Using viruses to treat cancer is exciting and novel and in principle can be used for a broad variety of tumors. However, the approach is distinctly different from other cancer therapies since success depends on establishment of an infection within the tumor and ongoing propagation of the oncolytic virus within the tumor itself. Therefore, the target itself amplifies the therapy. This introduces complex dynamics especially when the immune system is taken into consideration as well as the physical and other biological barriers to virus growth. Understanding these dynamics not only requires mathematical and computational models but also approaches for the noninvasive monitoring of the virus and tumor populations. In this perspective, we discuss strategies and current results to achieve this important goal of understanding these dynamics in pursuit of optimization of oncolytic virotherapy.

Applications of nuclear-based imaging in gene and cell therapy: probe considerations

Several types of gene- and cell-based therapeutics are now emerging in the cancer immunotherapy, transplantation, and regenerative medicine landscapes. Radionuclear-based imaging can be used as a molecular imaging tool for repetitive and non-invasive visualization as well as in vivo monitoring of therapy success. In this review, we discuss the principles of nuclear-based imaging and provide a comprehensive overview of its application in gene and cell therapy. This review aims to inform investigators in the biomedical field as well as clinicians on the state of the art of nuclear imaging, from probe design to available radiopharmaceuticals and advances of direct (probe-based) and indirect (transgene-based) strategies in both preclinical and clinical settings. Notably, as the nuclear-based imaging toolbox is continuously expanding, it will be increasingly incorporated into the clinical setting where the distribution, targeting, and persistence of a new generation of therapeutics can be imaged and ultimately guide therapeutic decisions.

Tumor microenvironment affects exogenous sodium/iodide symporter expression

For decades, sodium/iodide symporter NIS-mediated iodide uptake has played a crucial role in the radioactive ablation of thyroid cancer cells. NIS-based gene therapy has also become a promising tool for the treatment of tumors of extrathyroidal origin. But its applicability has been hampered by reduced expression of NIS, resulting in a moderated capacity to accumulate 131I and in inefficient ablation. Despite numerous preclinical enhancement strategies, the understanding of NIS expression within tumors remains limited. This study aims at a better understanding of the functional behavior of exogenous NIS expression in the context of malignant solid tumors that are characterized by rapid growth with an insufficient vasculature, leading to hypoxia and quiescence. Using subcutaneous HT29NIS and K7M2NIS tumors, we show that NIS-mediated uptake and NIS expression at the plasma membrane of cancer cells are impaired in the intratumoral regions. For a better understanding of the underlying molecular mechanisms induced by hypoxia and quiescence (separately and in combination), we performed experiments on HT29NIS cancer cells. Hypoxia and quiescence were both found to impair NIS-mediated uptake through mechanisms including NIS mis-localization. Modifications in the expression of proteins and metabolites involved in plasma membrane localization and in energy metabolism were found using untargeted proteomics and metabolomics approaches. In conclusion, our results provide evidence that hypoxia and quiescence impair NIS expression at the plasma membrane, and iodide uptake. Our study also shows that the tumor microenvironment is an important parameter for successful NIS-based cancer treatment.

In Vivo Imaging of Oncolytic Measles Virus Propagation with Single-Cell Resolution

Recombinant measles viruses (MVs) have oncolytic activity against a variety of human cancers. However, their kinetics of spread within tumors has been unexplored. We established an intravital imaging system using the dorsal skin fold chamber, which allows for serial, non-invasive imaging of tumor cells and replication of a fusogenic and a hypofusogenic MV. Hypofusogenic virus-infected cells were detected at the earliest 3 days post-infection (dpi), with peak infection around 6 dpi. In contrast, the fusogenic virus replicated faster: infected cells were detectable 1 dpi and cells were killed quickly. Infection foci were significantly larger with the fusogenic virus. Both viruses formed syncytia. The spatial relationships between cells have a major influence on the outcome of therapy with oncolytic viruses.

Regression of experimental NIS-expressing breast cancer brain metastases in response to radioiodide/gemcitabine dual therapy

Treating breast cancer brain metastases (BCBMs) is challenging. Na⁺/I⁻ symporter (NIS) expression in BCBMs would permit their selective targeting with radioiodide (¹³¹I⁻). We show impressive enhancement of tumor response by combining¹³¹I⁻ with gemcitabine (GEM), a cytotoxic radiosensitizer. Nude mice mammary fat-pad (MFP) tumors and BCBMs were generated with braintropic MDA-MB-231Br cells transduced with bicistronically-linked NIS and firefly luciferase cDNAs. Response was monitored in vivo via bioluminescent imaging and NIS tumor expression.¹³¹I⁻/GEM therapy inhibited MFP tumor growth more effectively than either agent alone. BCBMs were treated with: high or low-dose GEM (58 or 14.5 mg/Kg×4); ¹³¹I⁻ (1mCi or 2×0.5 mCi 7 days apart); and ¹³¹I⁻/GEM therapy. By post-injection day (PID) 25, 82-86% of controls and 78-83% of ¹³¹I⁻-treated BCBM grew, whereas 17% low-dose and 36% high-dose GEM regressed. The latter tumors were smaller than the controls with comparable NIS expression (~20% of cells). High and low-dose ¹³¹I⁻/GEM combinations caused 89% and 57% tumor regression, respectively. High-dose GEM/¹³¹I⁻ delayed tumor growth: tumors increased 5-fold in size by PID45 (controls by PID18). Although fewer than 25% of cells expressed NIS, GEM/¹³¹I⁻ caused dramatic tumor regression in NIS-transduced BCBMs. This effect was synergistic, and supports the hypothesis that GEM radiosensitizes cells to ¹³¹I⁻.

Human sodium iodide transporter gene-mediated imaging and therapy of mouse glioma, comparison between 188Re and 131I

Novel treatment options are urgently required for patients with glioma who are not effectively treated through standard therapy. Human sodium iodide symporter (hNIS) is a molecular target of certain tumors types. Compared with ¹³¹I, ¹⁸⁸Re possesses a higher energy and shorter half-life; therefore, the effects of ¹⁸⁸Re and ¹³¹I were compared in hNIS-mediated gene imaging and therapy in the present study. Recombinant human brain glioma cell line U87 was transfected with a recombinant lentiviral vector containing hNIS (U87-hNIS). U87-0 cell line transfected with blank lentivirus was prepared as a control. In vitro, the ¹⁸⁸Re and ¹³¹I uptake of U87-hNIS cells were 21.3-times and 25.9-times that of the control groups, however the excretion rate of the two nuclides was very rapid, and the half-life was only ~4 min. Sodium perchlorate inhibited hNIS-mediated ¹⁸⁸Re and ¹³¹I uptake to levels observed in the control groups. ¹⁸⁸Re and ¹³¹I were able to kill U87-hNIS cells selectively, with a survival of only 21.6 and 36.2%, respectively. U87-hNIS nude mice appeared to accumulate ¹⁸⁸Re, with a ratio of radioactivity counts between tumor and non-tumor sites of ~13.5 compared with 10.3 of ¹³¹I 1 h after radionuclide injection. In contrast with in vitro studies, U87-hNIS cells demonstrated a notable increase in ¹⁸⁸Re retention in vivo, even 24 h after ¹⁸⁸Re injection. U87-hNIS cells also exhibited increased ¹³¹I retention in vivo; however, as the time increased, ¹³¹I was rapidly released with the tumor no longer able to be imaged 24 h after ¹³¹I injection. Following treatment, U87-hNIS tumors experienced a volume reduction of 24.1%, whereas U87-0 cells demonstrated an increase of 28.8%. ¹⁸⁸Re and ¹³¹I were revealed to be effective at decreasing tumor volume compared with the control. However, ¹⁸⁸Re was significantly more potent compared with ¹³¹I (P<0.01). The present study indicated that the U87-hNIS cell line is sufficient to induce specific ¹⁸⁸Re and ¹³¹I uptake, which may kill cells in vitro and in vivo. ¹⁸⁸Re exhibited an increased retention time in vivo compared with ¹³¹I, which facilitates the imaging and therapy of U87-hNIS tumors.

Establishment of an Effective Radioiodide Thyroid Ablation Protocol in Mice

Due to the high variance in available protocols on iodide-131 ((131)I) ablation in rodents, we set out to establish an effective method to generate a thyroid-ablated mouse model that allows the application of the sodium iodide symporter (NIS) as a reporter gene without interference with thyroidal NIS. We tested a range of (131)I doses with and without prestimulation of thyroidal radioiodide uptake by a low-iodine diet and thyroid-stimulating hormone (TSH) application. Efficacy of induction of hypothyroidism was tested by measurement of serum T4 concentrations, pituitary TSHβ and liver deiodinase type 1 (DIO1) mRNA expression, body weight analysis, and (99m)Tc-pertechnetate scintigraphy. While 200 µCi (7.4 MBq) (131)I alone was not sufficient to abolish thyroidal T4 production, 500 µCi (18.5 MBq) (131)I combined with 1 week of a low-iodine diet decreased serum concentrations below the detection limit. However, the high (131)I dose resulted in severe side effects. A combination of 1 week of a low-iodine diet followed by injection of bovine TSH before the application of 150 µCi (5.5 MBq) (131)I decreased serum T4 concentrations below the detection limit and significantly increased pituitary TSHβ concentrations. The systemic effects of induced hypothyroidism were shown by growth arrest and a decrease in liver DIO1 expression below the detection limit. (99m)Tc-pertechnetate scintigraphy revealed absence of thyroidal (99m)Tc-pertechnetate uptake in ablated mice. In summary, we report a revised protocol for radioiodide ablation of the thyroid gland in the mouse to generate an in vivo model that allows the study of thyroid hormone action using NIS as a reporter gene.

Gene delivery in malignant B cells using the combination of lentiviruses conjugated to anti-transferrin receptor antibodies and an immunoglobulin promoter

BACKGROUND

We previously developed an antibody-avidin fusion protein (ch128.1Av) specific for the human transferrin receptor 1 (TfR1; CD71) to be used as a delivery vector for cancer therapy and showed that ch128.1Av delivers the biotinylated plant toxin saporin-6 into malignant B cells. However, as a result of widespread expression of TfR1, delivery of the toxin to normal cells is a concern. Therefore, we explored the potential of a dual targeted lentiviral-mediated gene therapy strategy to restrict gene expression to malignant B cells. Targeting occurs through the use of ch128.1Av or its parental antibody without avidin (ch128.1) and through transcriptional regulation using an immunoglobulin promoter.

METHODS

Flow cytometry was used to detect the expression of enhanced green fluorescent protein (EGFP) in a panel of cell lines. Cell viability after specific delivery of the therapeutic gene FCU1, a chimeric enzyme consisting of cytosine deaminase genetically fused to uracil phosphoribosyltransferse that converts the 5-fluorocytosine (5-FC) prodrug into toxic metabolites, was monitored using the MTS or WST-1 viability assay.

RESULTS

We found that EGFP was specifically expressed in a panel of human malignant B-cell lines, but not in human malignant T-cell lines. EGFP expression was observed in all cell lines when a ubiquitous promoter was used. Furthermore, we show the decrease of cell viability in malignant plasma cells in the presence of 5-FC and the FCU1 gene.

CONCLUSIONS

The present study demonstrates that gene expression can be restricted to malignant B cells and suggests that this dual targeted gene therapy strategy may help to circumvent the potential side effects of certain TfR1-targeted protein delivery approaches.

RNA-based viral vectors

The advent of reverse genetic approaches to manipulate the genomes of both positive (+) and negative (-) sense RNA viruses allowed researchers to harness these genomes for basic research. Manipulation of positive sense RNA virus genomes occurred first largely because infectious RNA could be transcribed directly from cDNA versions of the RNA genomes. Manipulation of negative strand RNA virus genomes rapidly followed as more sophisticated approaches to provide RNA-dependent RNA polymerase complexes coupled with negative-strand RNA templates were developed. These advances have driven an explosion of RNA virus vaccine vector development. That is, development of approaches to exploit the basic replication and expression strategies of RNA viruses to produce vaccine antigens that have been engineered into their genomes. This study has led to significant preclinical testing of many RNA virus vectors against a wide range of pathogens as well as cancer targets. Multiple RNA virus vectors have advanced through preclinical testing to human clinical evaluation. This review will focus on RNA virus vectors designed to express heterologous genes that are packaged into viral particles and have progressed to clinical testing.

Theranostic studies of human sodium iodide symporter imaging and therapy using 188Re: a human glioma study in mice

Objective

To investigate the role of ¹⁸⁸Re in human sodium iodide symporter (hNIS) theranostic gene-mediated human glioma imaging and therapy in model mice.

Methods

The human glioma cell line U87 was transfected with recombinant lentivirus encoding the hNIS gene under the control of cytomegalovirus promoter (U87-hNIS). The uptake and efflux of ¹⁸⁸Re were determined after incubating the cells with ¹⁸⁸Re. ¹⁸⁸Re uptake experiments in the presence of various concentrations of sodium perchlorate were carried out. In vitro cell killing tests with ¹⁸⁸Re were performed. U87-hNIS mediated ¹⁸⁸Re distribution, imaging and therapy in nude mice were also tested.

Results

U87-hNIS cell line was successfully established. The uptake of ¹⁸⁸Re in U87-hNIS cells increased up to 26-fold compared to control cells, but was released rapidly with a half-life of approximately 4 minutes. Sodium perchlorate reduced hNIS-mediated ¹⁸⁸Re uptake to levels of control cell lines. U87-hNIS cells were selectively killed following exposure to ¹⁸⁸Re, with a survival of 21.4%, while control cells had a survival of 92.1%. Unlike in vitro studies, U87-hNIS tumor showed a markedly increased ¹⁸⁸Re retention even 48 hours after ¹⁸⁸Re injection. In the therapy study, there was a significant difference in tumor size between U87-hNIS mice (317±67 mm³) and control mice (861±153 mm³) treated with ¹⁸⁸Re for 4 weeks (P<0.01).

Conclusion

The results indicate that inserting the hNIS gene into U87 cells is sufficient to induce specific ¹⁸⁸Re uptake, which has a cell killing effect both in vitro and in vivo. Moreover, our study, based on the function of hNIS as a theranostic gene allowing noninvasive imaging of hNIS expression by ¹⁸⁸Re scintigraphy, provides detailed characterization of in vivo vector biodistribution and level, localization, essential prerequisites for precise planning and monitoring of clinical gene therapy that aims to individualize gene therapy concept.

Objective assessment of image quality VI: imaging in radiation therapy

Earlier work on objective assessment of image quality (OAIQ) focused largely on estimation or classification tasks in which the desired outcome of imaging is accurate diagnosis. This paper develops a general framework for assessing imaging quality on the basis of therapeutic outcomes rather than diagnostic performance. By analogy to receiver operating characteristic (ROC) curves and their variants as used in diagnostic OAIQ, the method proposed here utilizes the therapy operating characteristic or TOC curves, which are plots of the probability of tumor control versus the probability of normal-tissue complications as the overall dose level of a radiotherapy treatment is varied. The proposed figure of merit is the area under the TOC curve, denoted AUTOC. This paper reviews an earlier exposition of the theory of TOC and AUTOC, which was specific to the assessment of image-segmentation algorithms, and extends it to other applications of imaging in external-beam radiation treatment as well as in treatment with internal radioactive sources. For each application, a methodology for computing the TOC is presented. A key difference between ROC and TOC is that the latter can be defined for a single patient rather than a population of patients.

The Na+/I- symporter (NIS): mechanism and medical impact

The Na(+)/I(-) symporter (NIS) is the plasma membrane glycoprotein that mediates active I(-) transport in the thyroid and other tissues, such as salivary glands, stomach, lactating breast, and small intestine. In the thyroid, NIS-mediated I(-) uptake plays a key role as the first step in the biosynthesis of the thyroid hormones, of which iodine is an essential constituent. These hormones are crucial for the development of the central nervous system and the lungs in the fetus and the newborn and for intermediary metabolism at all ages. Since the cloning of NIS in 1996, NIS research has become a major field of inquiry, with considerable impact on many basic and translational areas. In this article, we review the most recent findings on NIS, I(-) homeostasis, and related topics and place them in historical context. Among many other issues, we discuss the current outlook on iodide deficiency disorders, the present stage of understanding of the structure/function properties of NIS, information gleaned from the characterization of I(-) transport deficiency-causing NIS mutations, insights derived from the newly reported crystal structures of prokaryotic transporters and 3-dimensional homology modeling, and the novel discovery that NIS transports different substrates with different stoichiometries. A review of NIS regulatory mechanisms is provided, including a newly discovered one involving a K(+) channel that is required for NIS function in the thyroid. We also cover current and potential clinical applications of NIS, such as its central role in the treatment of thyroid cancer, its promising use as a reporter gene in imaging and diagnostic procedures, and the latest studies on NIS gene transfer aimed at extending radioiodide treatment to extrathyroidal cancers, including those involving specially engineered NIS molecules.

Systemic image-guided liver cancer radiovirotherapy using dendrimer-coated adenovirus encoding the sodium iodide symporter as theranostic gene

Currently, major limitations for the clinical application of adenovirus-mediated gene therapy are high prevalence of neutralizing antibodies, widespread expression of the coxsackie-adenovirus receptor (CAR), and adenovirus sequestration by the liver. In the current study, we used the sodium iodide symporter (NIS) as a theranostic gene to investigate whether coating of adenovirus with synthetic dendrimers could be useful to overcome these hurdles in order to develop adenoviral vectors for combination of systemic oncolytic virotherapy and NIS-mediated radiotherapy.

METHODS

We coated replication-deficient (Ad5-CMV/NIS) (CMV is cytomegalovirus) and replication-selective (Ad5-E1/AFP-E3/NIS) adenovirus serotype 5 carrying the hNIS gene with poly(amidoamine) dendrimers generation 5 (PAMAM-G5) in order to investigate transduction efficacy and altered tropism of these coated virus particles by (123)I scintigraphy and to evaluate their therapeutic potential for systemic radiovirotherapy in a liver cancer xenograft mouse model.

RESULTS

After dendrimer coating, Ad5-CMV/NIS demonstrated partial protection from neutralizing antibodies and enhanced transduction efficacy in CAR-negative cells in vitro. In vivo (123)I scintigraphy of nude mice revealed significantly reduced levels of hepatic transgene expression after intravenous injection of dendrimer-coated Ad5-CMV/NIS (dcAd5-CMV/NIS). Evasion from liver accumulation resulted in significantly reduced liver toxicity and increased transduction efficiency of dcAd5-CMV/NIS in hepatoma xenografts. After PAMAM-G5 coating of the replication-selective Ad5-E1/AFP-E3/NIS, a significantly enhanced oncolytic effect was observed after intravenous application (virotherapy) that was further increased by additional treatment with a therapeutic dose of (131)I (radiovirotherapy) and was associated with markedly improved survival.

CONCLUSION

These results demonstrate efficient liver detargeting and tumor retargeting of adenoviral vectors after coating with synthetic dendrimers, thereby representing a promising innovative strategy for systemic NIS gene therapy. Moreover, our study-based on the function of NIS as a theranostic gene allowing the noninvasive imaging of NIS expression by (123)I scintigraphy-provides detailed characterization of in vivo vector biodistribution and localization, level, and duration of transgene expression, essential prerequisites for exact planning and monitoring of clinical gene therapy trials that aim to individualize the NIS gene therapy concept.

Sodium iodide symporter (NIS)-mediated radiovirotherapy of hepatocellular cancer using a conditionally replicating adenovirus. Gene Ther. 2013;20:625-633. [PMID: 23038026 DOI: 10.1038/gt.2012.79]

In this study, we determined the in vitro and in vivo efficacy of sodium iodide symporter (NIS) gene transfer and the therapeutic potential of oncolytic virotherapy combined with radioiodine therapy using a conditionally replicating oncolytic adenovirus. For this purpose, we used a replication-selective adenovirus in which the E1a gene is driven by the mouse alpha-fetoprotein (AFP) promoter and the human NIS gene is inserted in the E3 region (Ad5-E1/AFP-E3/NIS). Human hepatocellular carcinoma cells (HuH7) infected with Ad5-E1/AFP-E3/NIS concentrated radioiodine at a level that was sufficiently high for a therapeutic effect in vitro. In vivo experiments demonstrated that 3 days after intratumoral (i.t.) injection of Ad5-E1/AFP-E3/NIS HuH7 xenograft tumors accumulated approximately 25% ID g(-1) (percentage of the injected dose per gram tumor tissue) (123)I as shown by (123)I gamma camera imaging. A single i.t. injection of Ad5-E1/AFP-E3/NIS (virotherapy) resulted in a significant reduction of tumor growth and prolonged survival, as compared with injection of saline. Combination of oncolytic virotherapy with radioiodine treatment (radiovirotherapy) led to an additional reduction of tumor growth that resulted in markedly improved survival as compared with virotherapy alone. In conclusion, local in vivo NIS gene transfer using a replication-selective oncolytic adenovirus is able to induce a significant therapeutic effect, which can be enhanced by additional (131)I application.

The sodium iodide symporter (NIS) as an imaging reporter for gene, viral, and cell-based therapies

Preclinical and clinical tomographic imaging systems increasingly are being utilized for non-invasive imaging of reporter gene products to reveal the distribution of molecular therapeutics within living subjects. Reporter gene and probe combinations can be employed to monitor vectors for gene, viral, and cell-based therapies. There are several reporter systems available; however, those employing radionuclides for positron emission tomography (PET) or singlephoton emission computed tomography (SPECT) offer the highest sensitivity and the greatest promise for deep tissue imaging in humans. Within the category of radionuclide reporters, the thyroidal sodium iodide symporter (NIS) has emerged as one of the most promising for preclinical and translational research. NIS has been incorporated into a remarkable variety of viral and non-viral vectors in which its functionality is conveniently determined by in vitro iodide uptake assays prior to live animal imaging. This review on the NIS reporter will focus on 1) differences between endogenous NIS and heterologously-expressed NIS, 2) qualitative or comparative use of NIS as an imaging reporter in preclinical and translational gene therapy, oncolytic viral therapy, and cell trafficking research, and 3) use of NIS as an absolute quantitative reporter.

Curative one-shot systemic virotherapy in murine myeloma

Current therapy for multiple myeloma is complex and prolonged. Antimyeloma drugs are combined in induction, consolidation and/or maintenance protocols to destroy bulky disease, then suppress or eradicate residual disease. Oncolytic viruses have the potential to mediate both tumor debulking and residual disease elimination, but this curative paradigm remains unproven. Here we engineered an oncolytic vesicular stomatitis virus to minimize its neurotoxicity, enhance induction of antimyeloma immunity, and facilitate noninvasive monitoring of its intratumoral spread. Using high resolution imaging, autoradiography and immunohistochemistry, we demonstrate that the intravenously administered virus extravasates from tumor blood vessels in immunocompetent myeloma-bearing mice, nucleating multiple intratumoral infectious centers which expand rapidly and necrose at their centers, ultimately coalescing to cause extensive tumor destruction. This oncolytic tumor debulking phase lasts only for 72 hours after virus administration, and is completed before antiviral antibodies become detectable in the bloodstream. Anti-myeloma T cells, cross-primed as the virus-infected cells provoke an antiviral immune response, then eliminate residual uninfected myeloma cells. The study establishes a curative oncolytic paradigm for multiple myeloma where direct tumor debulking and immune eradication of minimal disease are mediated by a single intravenous dose of a single therapeutic agent. Clinical translation is underway.

Evaluation of lentiviral-mediated expression of sodium iodide symporter in anaplastic thyroid cancer and the efficacy of in vivo imaging and therapy

Anaplastic thyroid carcinoma (ATC) is one of the most deadly cancers. With intensive multimodalities of treatment, the survival remains low. ATC is not sensitive to ¹³¹I therapy due to loss of sodium iodide symporter (NIS) gene expression. We have previously generated a stable human NIS-expressing ATC cell line, ARO, and the ability of iodide accumulation was restored. To make NIS-mediated gene therapy more applicable, this study aimed to establish a lentiviral system for transferring hNIS gene to cells and to evaluate the efficacy of in vitro and in vivo radioiodide accumulation for imaging and therapy. Lentivirus containing hNIS cDNA were produced to transduce ARO cells which do not concentrate iodide. Gene expression, cell function, radioiodide imaging and treatment were evaluated in vitro and in vivo. Results showed that the transduced cells were restored to express hNIS and accumulated higher amount of radioiodide than parental cells. Therapeutic dose of ¹³¹I effectively inhibited the tumor growth derived from transduced cells as compared to saline-treated mice. Our results suggest that the lentiviral system efficiently transferred and expressed hNIS gene in ATC cells. The transduced cells showed a promising result of tumor imaging and therapy.

Mesenchymal Stem Cell-mediated delivery of the sodium iodide symporter supports radionuclide imaging and treatment of breast cancer

Mesenchymal Stem Cells (MSCs) migrate specifically to tumors in vivo, and coupled with their capacity to bypass immune surveillance, are attractive vehicles for tumor-targeted delivery of therapeutic agents. This study aimed to introduce MSC-mediated expression of the sodium iodide symporter (NIS) for imaging and therapy of breast cancer. Tumor bearing animals received an intravenous or intratumoral injection of NIS expressing MSCs (MSC-NIS), followed by (99m) Technetium pertechnetate imaging 3-14 days later using a BazookaSPECT γ-camera. Tissue was harvested for analysis of human NIS (hNIS) expression by relative quantitative-polymerase chain reaction. Therapy animals received an i.p. injection of (131) I or saline 14 days after injection of MSC-NIS, and tumor volume was monitored for 8 weeks. After injection of MSC-NIS, BazookaSPECT imaging revealed an image of animal intestines and chest area at day 3, along with a visible weak tumor image. By day 14, the tumor was visible with a significant reduction in radionuclide accumulation in nontarget tissue observed. hNIS gene expression was detected in the intestines, heart, lungs, and tumors at early time points but later depleted in nontarget tissues and persisted at the tumor site. Based on imaging/biodistribution data, animals received a therapeutic dose of (131) I 14 days after MSC-NIS injection. This resulted in a significant reduction in tumor growth (mean ± SEM, 236 ± 62 mm(3) vs. 665 ± 204 mm(3) in controls). The ability to track MSC migration and transgene expression noninvasively in real time before therapy is a major advantage to this strategy. This promising data supports the feasibility of this approach as a novel therapy for breast cancer.

Telomerase-driven expression of the sodium iodide symporter (NIS) for in vivo radioiodide treatment of cancer: a new broad-spectrum NIS-mediated antitumor approach

CONTEXT

Telomerase promoters (hTERT and hTR) are useful for transcriptional targeting in gene therapy models of cancer. Telomerase-driven expression of the sodium iodide symporter (NIS) in tumor cells has been successfully used as a reporter gene in vivo using positron emission tomography (PET) imaging.

OBJECTIVE

The aim of this study was to investigate the NIS-mediated therapeutic effect of telomerase promoters in a wide variety of human cancer cell lines.

DESIGN AND METHODS

Promoter fragments from either hTERT or hTR were used to drive the expression of NIS in cell lines derived from melanoma (M14), breast (MDA-MB-231), colon (HT-29), lung (H460), ovarian (OVCAR-3), and thyroid (TPC-1) carcinomas. Iodide uptake assays, protein immunodetection, and clonigenic assays were used to confirm NIS functional expression and the (131)I-mediated cytopathic effect. Tumor xenografts in mice were infected with hTERT and hTR and then treated using radioiodide.

RESULTS

Both promoters were selectively active in cancer cells that were effectively killed by exposure to (131)I. One single dose of 1 mCi (131)I markedly suppressed tumor growth of melanoma-derived tumor xenografts compared with controls. This effect was more modest in colon cancer-derived xenografts in part due to the reduced infectivity and the tumor cystic nature. The therapeutic effect of hTR promoter was found to be stronger than that of hTERT promoter.

CONCLUSIONS

These results demonstrate that telomerase-driven expression of NIS could potentially have applications for (131)I therapy of a wide variety of cancers. Additionally, this is the first study to report NIS-mediated (131)I therapy of melanoma tumors in vivo.

Sodium iodide symporter (NIS)-mediated radionuclide ((131)I, (188)Re) therapy of liver cancer after transcriptionally targeted intratumoral in vivo NIS gene delivery

We reported the therapeutic efficacy of (131)I in hepatocellular carcinoma (HCC) cells stably expressing the sodium iodide symporter (NIS) under the control of the tumor-specific α-fetoprotein (AFP) promoter. In the current study we investigated the efficacy of adenovirus-mediated in vivo NIS gene transfer followed by (131)I and (188)Re administration for the treatment of HCC xenografts. We used a replication-deficient adenovirus carrying the human NIS gene linked to the mouse AFP promoter (Ad5-AFP-NIS) for in vitro and in vivo NIS gene transfer. Functional NIS expression was confirmed by in vivo γ-camera imaging, followed by analysis of NIS protein and mRNA expression. Human HCC (HepG2) cells infected with Ad5-AFP-NIS concentrated 50% of the applied activity of (125)I, which was sufficiently high for a therapeutic effect in an in vitro clonogenic assay. Four days after intratumoral injection of Ad5-AFP-NIS (3×10(9) plaque-forming units) HepG2 xenografts accumulated 14.5% injected dose (ID)/g (123)I with an effective half-life of 13 hr (tumor-absorbed dose, 318 mGy/MBq (131)I). In comparison, 9.2% ID/g (188)Re was accumulated in tumors with an effective half-life of 12.8 hr (tumor-absorbed dose, 545 mGy/MBq). After adenovirus-mediated NIS gene transfer in HepG2 xenografts administration of a therapeutic dose of (131)I or (188)Re (55.5 MBq) resulted in a significant delay in tumor growth and improved survival without a significant difference between (188)Re and (131)I. In conclusion, a therapeutic effect of (131)I and (188)Re was demonstrated in HepG2 xenografts after tumor-specific adenovirus-mediated in vivo NIS gene transfer.

Sodium butyrate enhances the expression of baculovirus-mediated sodium/iodide symporter gene in A549 lung adenocarcinoma cells

OBJECTIVE

Increased expression of sodium/iodide symporter (NIS) is required for reporter gene imaging and effective radioiodine treatment of tumor. We investigated whether increased accumulation of iodine can be induced by sodium butyrate through a newly developed baculoviral transfer of the human NIS (hNIS) gene in A549 human lung adenocarcinoma.

METHODS

A recombinant baculovirus [Bac-cytomegalovirus (CMV)-hNIS] encoding hNIS gene under the control of the CMV promoter was constructed. After A549 cells were transfected with Bac-CMV-hNIS in the presence of sodium butyrate, the expression of hNIS protein was detected by immunofluorescence and western blot analysis. The uptake and efflux of iodine were determined after the incubation of the transfected cells with I-iodide in the presence or absence of sodium butyrate.

RESULTS

Immunocytochemical staining and western blot analysis showed increased hNIS protein expression in A549 cells transfected with Bac-CMV-hNIS after sodium butyrate treatment. Bac-CMV-hNIS transfected A549 cells accumulated up to about nine times more I than nontransfected cells; the amount of I uptake increased in a sodium butyrate in dose-dependent manner (P<0.001). However, rapid efflux of radioactivity was observed, with 50% lost during the first 2 min after I-containing medium had been replaced by a nonradioactive medium.

CONCLUSION

Our results indicated that an improved efficiency of baculovirus-mediated hNIS reporter gene imaging in lung adenocarcinoma is possible with treatment with sodium butyrate. However, additional conditions need to be defined to reduce the rapid efflux of radioiodine for the purpose of radionuclide therapy.

Baculovirus vector-mediated transfer of NIS gene into colon tumor cells for radionuclide therapy

AIM: To investigate the feasibility of radionuclide therapy of colon tumor cells by baculovirus vector-mediated transfer of the sodium/iodide symporter (NIS) gene.

METHODS: A recombinant baculovirus plasmid carrying the NIS gene was constructed, and the viruses (Bac-NIS) were prepared using the Bac-to-Bac system. The infection efficiency in the colon cancer cell line SW1116 of a green fluorescent protein (GFP) expressing baculovirus (Bac-GFP) at different multiplicities of infection (MOI) with various concentrations of sodium butyrate was determined by flow cytometry. An in vitro cytotoxicity assay was also conducted after infection of SW1116 cells with Bac-NIS. Iodine uptake of Bac-NIS infected SW1116 cells and inhibition of this uptake by sodium perchlorate was examined, and the effect of Bac-NIS-mediated ¹³¹I in killing tumor cells was evaluated by cell colony formation tests.

RESULTS: Infection and transgene expression in SW1116 with Bac-GFP were significantly enhanced by sodium butyrate, as up to 72% of SW1116 cells were infected with the virus at MOI of 400 and sodium butyrate at 0.5 mmol/L. No obvious cytotoxicity was observed under these conditions. Infection of SW1116 with Bac-NIS allowed uptake of ¹³¹I in these tumor cells, which could be inhibited by sodium perchlorate. The viability of SW1116 cells infected with Bac-NIS was significantly lower than with Bac-GFP, suggesting that NIS gene-mediated ¹³¹I uptake could specifically kill tumor cells.

CONCLUSION: Baculovirus vector-mediated NIS gene therapy is a potential approach for treatment of colon cancer.

Sodium iodide symporter (NIS)-mediated radiovirotherapy for pancreatic cancer.AJR Am J Roentgenol. 2010;195:341-349. [PMID: 20651188 DOI: 10.2214/AJR.09.3672]

OBJECTIVE

We have previously shown the therapeutic efficacy of an engineered oncolytic measles virus expressing the sodium iodide symporter reporter gene (MV-NIS) in mice with human pancreatic cancer xenografts. The goal of this study was to determine the synergy between MV-NIS-induced oncolysis and NIS-mediated (131)I radiotherapy in this tumor model.

MATERIALS AND METHODS

Subcutaneous human BxPC-3 pancreatic tumors were injected twice with MV-NIS. Viral infection, NIS expression, and intratumoral iodide uptake were quantitated with (123)I micro-SPECT/CT. Mice with MV-NIS-infected tumors were treated with 0, 37, or 74 MBq (131)I and monitored for tumor progression and survival. Additional studies were performed with stable NIS-expressing tumors (BxPC-3-NIS) treated with 0, 3.7, 18.5, 37, or 74 MBq of (131)I.

RESULTS

Mice treated with intratumoral MV-NIS exhibited significant tumor growth delay (p < 0.01) and prolonged survival (p = 0.02) compared with untreated mice. Synergy between MV-NIS-induced oncolysis and NIS-mediated (131)I ablation was not seen; however, a significant correlation was observed between NIS-mediated intratumoral iodide localization (% ID/g) and peak tumor volume reduction (p = 0.04) with combination MV-NIS and (131)I therapy. Stably transduced NIS-expressing BxPC-3 tumors exhibited rapid regression with > or = 18.5 MBq (131)I.

CONCLUSION

Delivery of (131)I radiotherapy to NIS-expressing tumors can be optimized using micro-SPECT/CT imaging guidance. Significant hurdles exist for NIS as a therapeutic gene for combined radiovirotherapy in this human pancreatic cancer model. The lack of synergy observed with MV-NIS and (131)I in this model was not due to a lack of radiosensitivity but rather to a nonuniform intratumoral distribution of MV-NIS infection.

Genetics and phenomics of hypothyroidism and goiter due to NIS mutations

Molecular cloning of the NIS gene in 1996 allowed examination of the molecular basis of congenital hypothyroidism due to iodide transport defect (ITD) many years after the first case was described by Federman et al. in 1958. Since 1997, when the first NIS mutation causing ITD was identified and characterized, 12 different NIS molecular defects have been described in 31 ITD patients. Interestingly, marked clinical heterogeneity between patients with the same NIS mutation and in patients with different mutations in the NIS gene without a clear genotype-phenotype correlation has been observed. The study of NIS mutations as the molecular basis of ITD has not only yielded extremely valuable structure/function information on NIS, but has also provided an important tool for preclinical diagnosis and genetic counseling of ITD patients.

Sodium iodide symporter and the radioiodine treatment of thyroid carcinoma

Since the specific accumulation of iodide in thyroid was found in 1915, radioiodine has been widely applied to diagnose and treat thyroid cancer. Iodide uptake occurs across the membrane of the thyroid follicular cells and cancer cells through an active transporter process mediated by the sodium iodide symporter (NIS). The NIS coding genes were cloned and identified from rat and human in 1996. Evaluation of the NIS gene and protein expression is critical in the management of thyroid cancer, and several approaches have been tried to increase NIS levels. Identification of the NIS gene has provided a means of expanding its role in the radionuclide gene therapy of nonthyroidal cancers as well as thyroid cancer. In this article, we explain the relationship between NIS expression and the treatment of thyroid carcinoma with I-131, and we include a review of the results of our experimental and clinical trials.

Targeted radiotherapy for prostate cancer with an oncolytic adenovirus coding for human sodium iodide symporter

PURPOSE

Oncolytic adenoviruses are promising tools for cancer therapy. Although several clinical reports have indicated both safety and promising antitumor capabilities for these viruses, there are only a few examples of complete tumor eradication. Thus, the antitumor efficacy of oncolytic adenoviruses needs to be improved. One potentially useful approach is combination with radiotherapy.

EXPERIMENTAL DESIGN

To target systemically administered radioiodide to tumors, we created Ad5/3-Delta24-human sodium iodide symporter (hNIS), a Rb-p16 pathway selective infectivity enhanced oncolytic adenovirus encoding hNIS.

RESULTS

Ad5/3-Delta24-hNIS replication effectively killed prostate cancer cells in vitro and in vivo. Also, the virus-mediated radioiodide uptake into prostate cancer cells in vitro and into tumors in vivo. Furthermore, Ad5/3-Delta24-hNIS with radioiodide was significantly more effective than virus alone in mice with prostate cancer xenografts.

CONCLUSIONS

These results suggest that oncolytic adenovirus-mediated targeted radiotherapy might be a potentially useful option for enhancing the efficacy or adenoviral virotherapy.

Concordant activity of transgene expression cassettes inserted into E1, E3 and E4 cloning sites in the adenovirus genome

BACKGROUND

Expression cassettes can be inserted at several positions into recombinant adenoviral genomes but the implications of this choice for transgene expression level have not been determined. Knowledge of the relative expression levels of transgenes inserted at different sites in the adenoviral genome is of particular significance for transgene expression monitoring approaches that rely on the concordant expression of a marker transgene inserted elsewhere in the viral genome.

METHODS

Three expression cassettes, each comprising a cytomegalovirus promoter driving one of three marker peptides [serum carcinoembryonic antigen (sCEA), beta subunit of human chorionic gonadotropin (betahCG) or human sodium iodide symporter (hNIS)], were inserted into E1, E3 or E4 cloning sites in a recombinant adenoviral vector backbone. High titer stocks of bicistronic adenoviral vectors coding for combinations of marker peptides were prepared. A panel of human cells of various lineages was infected with the vectors and expression ratios of the transgene-encoded proteins were analysed. Serum levels of the soluble proteins and hepatic uptake of radioactive iodine were also compared in vivo in nude rats after intravenous vector infusion.

RESULTS

High concordance of expression between the inserted transgenes was observed in all of the bicistronic vectors irrespective of whether the expression cassettes were placed in the E1, E3 or E4 regions. Concordance was maintained across multiple cell lineages. In vivo, in athymic rats, blood and urine levels of betahCG were highly concordant with serum levels of sCEA at all timepoints after intravenous infusion of the bicistronic vectors encoding both of these soluble markers. Hepatic radioiodine uptake was concordant with serum CEA concentration in mice infused with a bicistronic vector expressing CEA and NIS.

CONCLUSIONS

The expression level of a given transgene in an adenoviral vector genome can be accurately and quantitatively inferred from the expression of a marker protein encoded by a second transgene inserted elsewhere in the vector genome.

Quantitative molecular imaging of viral therapy for pancreatic cancer using an engineered measles virus expressing the sodium-iodide symporter reporter gene

OBJECTIVE

Our objectives were to, first, determine the oncolytic potential of an engineered measles virus expressing the sodium-iodide symporter gene (MV-NIS) for intratumoral (i.t.) therapy of pancreatic cancer and, second, evaluate NIS as a reporter gene for in vivo monitoring and quantitation of MV-NIS delivery, viral spread, and gene expression in this tumor model.

MATERIALS AND METHODS

Cultured human pancreatic cancer cells were infected with MV-NIS. Light microscopy, cell viability, and iodide uptake assays were used to confirm viral infection and NIS gene expression and function in vitro. Human pancreatic tumor xenografts were established in mice and infected via i.t. MV-NIS injections. NIS-mediated i.t. iodide uptake was quantitated by (123)I micro-SPECT/CT. i.t. MV-NIS infection was confirmed by immunohistochemistry of excised pancreatic xenografts. The oncolytic efficacy of MV-NIS was determined by measurement of tumor growth and mouse survival.

RESULTS

Infection of human pancreatic cancer cell lines with MV-NIS in vitro resulted in syncytia formation, marked iodide uptake, and ultimately cell death. Tumor xenografts infected with MV-NIS concentrated radioiodine, allowing serial quantitative imaging with (123)I micro-SPECT/CT. i.t. MV-NIS therapy of human pancreatic cancer xenografts resulted in a significant reduction in tumor volume and increased survival time of the treated mice compared with the control mice.

CONCLUSION

MV-NIS efficiently infects human pancreatic tumor cells and results in sufficient radioiodine uptake to enable noninvasive serial imaging and quantitation of the intensity, distribution, and time course of NIS gene expression. MV-NIS also shows oncolytic activity in human pancreatic cancer xenografts: Tumor growth is reduced and survival is increased in mice treated with the virus.

Measles virus for cancer therapy

Measles virus offers an ideal platform from which to build a new generation of safe, effective oncolytic viruses. Occasional so-called spontaneous tumor regressions have occurred during natural measles infections, but common tumors do not express SLAM, the wild-type MV receptor, and are therefore not susceptible to the virus. Serendipitously, attenuated vaccine strains of measles virus have adapted to use CD46, a regulator of complement activation that is expressed in higher abundance on human tumor cells than on their nontransformed counterparts. For this reason, attenuated measles viruses are potent and selective oncolytic agents showing impressive antitumor activity in mouse xenograft models. The viruses can be engineered to enhance their tumor specificity, increase their antitumor potency, and facilitate noninvasive in vivo monitoring of their spread. A major impediment to the successful deployment of oncolytic measles viruses as anticancer agents is the high prevalence of preexisting anti-measles immunity, which impedes bloodstream delivery and curtails intratumoral virus spread. It is hoped that these problems can be addressed by delivering the virus inside measles-infected cell carriers and/or by concomitant administration of immunosuppressive drugs. From a safety perspective, population immunity provides an excellent defense against measles spread from patient to carers and, in 50 years of human experience, reversion of attenuated measles to a wild-type pathogenic phenotype has not been observed. Clinical trials testing oncolytic measles viruses as an experimental cancer therapy are currently underway.

Peroxisome proliferator-activated receptor gamma overexpression and knockdown: impact on human B cell lymphoma proliferation and survival

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a multifunctional transcription factor that regulates adipogenesis, immunity and inflammation. Our laboratory previously demonstrated that PPARgamma ligands induce apoptosis in malignant B cells. While malignant B lineage cells such as B cell lymphoma express PPARgamma, its physiological function remains unknown. Herein, we demonstrate that silencing PPARgamma expression by RNAi in human Burkitt's type B lymphoma cells increased basal and mitogen-induced proliferation and survival, which was accompanied by enhanced NF-kappaB activity and increased expression of Bcl-2. These cells also had increased survival upon exposure to PPARgamma ligands and exhibited a less differentiated phenotype. In contrast, PPARgamma overexpression in B lymphoma cells inhibited cell growth and decreased their proliferative response to mitogenic stimuli. These cells were also more sensitive to PPARgamma-ligand induced growth arrest and displayed a more differentiated phenotype. Collectively, these findings support a regulatory role for PPARgamma in the proliferation, survival and differentiation of malignant B cells. These findings further suggest the potential of PPARgamma as a therapeutic target for B cell malignancy.

The potential of 211Astatine for NIS-mediated radionuclide therapy in prostate cancer

PURPOSE

We reported recently the induction of selective iodide uptake in prostate cancer cells (LNCaP) by prostate-specific antigen (PSA) promoter-directed sodium iodide symporter (NIS) expression that allowed a significant therapeutic effect of (131)I. In the current study, we studied the potential of the high-energy alpha-emitter (211)At, also transported by NIS, as an alternative radionuclide after NIS gene transfer in tumors with limited therapeutic efficacy of (131)I due to rapid iodide efflux.

METHODS

We investigated uptake and therapeutic efficacy of (211)At in LNCaP cells stably expressing NIS under the control of the PSA promoter (NP-1) in vitro and in vivo.

RESULTS

NP-1 cells concentrated (211)At in a perchlorate-sensitive manner, which allowed a dramatic therapeutic effect in vitro. After intraperitoneal injection of (211)At (1 MBq), NP-1 tumors accumulated approximately 16% ID/g (211)At (effective half-life 4.6 h), which resulted in a tumor-absorbed dose of 1,580+/-345 mGy/MBq and a significant tumor volume reduction of up to 82+/-19%, while control tumors continued their growth exponentially.

CONCLUSIONS

A significant therapeutic effect of (211)At has been demonstrated in prostate cancer after PSA promoter-directed NIS gene transfer in vitro and in vivo suggesting a potential role for (211)At as an attractive alternative radioisotope for NIS-targeted radionuclide therapy, in particular in smaller tumors with limited radionuclide retention time.

Image-guided radioiodide therapy of medullary thyroid cancer after carcinoembryonic antigen promoter-targeted sodium iodide symporter gene expression

In contrast to follicular cell-derived thyroid cancer, medullary thyroid cancer (MTC) remains difficult to treat because of its unresponsiveness to radioiodine therapy, or to conventional chemo- and radiotherapy. We therefore examined the feasibility of radioiodine therapy of MTC after human sodium iodide symporter (hNIS) gene transfer, using the tumor-specific carcinoembryonic antigen (CEA) promoter for transcriptional targeting. NIS gene transfer was performed in vivo in human MTC cell (TT) xenografts, using adenoviral vectors carrying the NIS gene linked to the cytomegalovirus promoter (Ad5-CMV-NIS) or a CEA promoter fragment (Ad5-CEA-NIS). Functional NIS expression was confirmed by immunostaining as well as in vivo (123)I gamma-camera imaging followed by application of a therapeutic (131)I dose. TT cell xenografts in nude mice injected intratumorally with Ad5-CEA-NIS accumulated 7.5 +/- 1.2% ID/g (percentage injected dose per gram tumor tissue; 5 x 10(8) PFU) and 12 +/- 2.95% ID/g (1 x 10(9) PFU) with an average biological half-life of 6.1 +/- 0.8 and 23.6 +/- 3.7 hr, respectively, as compared with accumulation of 8.4 +/- 0.9% ID/g with a biological half-life of 12 +/- 8 hr after application of Ad5-CMV-NIS (5 x 10(8) PFU). After Ad5-CEA-NIS-mediated NIS gene transfer in TT cell xenografts administration of a therapeutic dose of 111 MBq (3 mCi) of (131)I resulted in a significant reduction of tumor growth associated with significantly lower calcitonin serum levels in treated mice as well as improved survival. We conclude that a therapeutic effect of (131)I was demonstrated in vivo in MTC cell xenografts after adenovirus-mediated induction of tumor-specific iodide accumulation by CEA promoter-directed hNIS expression.

Alpha-fetoprotein promoter-targeted sodium iodide symporter gene therapy of hepatocellular carcinoma

Due to limited treatment options the prognosis of patients with advanced hepatocellular cancer (HCC) has remained poor. To investigate an alternative therapeutic approach, we examined the feasibility of radioiodine therapy of HCC following human sodium iodide symporter (NIS) gene transfer using a mouse alpha-fetoprotein (AFP) promoter construct to target NIS expression to HCC cells. For this purpose, the murine Hepa 1-6 and the human HepG2 hepatoma cell lines were stably transfected with NIS cDNA under the control of the tumor-specific AFP promoter. The stably transfected Hepa 1-6 cell line showed a 10-fold increase in iodide accumulation, while HepG2 cells accumulated (125)I approximately 60-fold. Tumor-specific NIS expression was confirmed on mRNA level by northern blot analysis, and on protein level by immunostaining, that revealed primarily membrane-associated NIS-specific immunoreactivity. In an in vitro clonogenic assay up to 78% of NIS-transfected Hepa 1-6 and 93% of HepG2 cells were killed by (131)I exposure, while up to 96% of control cells survived. In vivo NIS-transfected HepG2 xenografts accumulated 15% of the total (123)I administered per gram tumor with a biological half-life of 8.38 h, resulting in a tumor absorbed dose of 171 mGy MBq(-1) (131)I. After administration of a therapeutic (131)I dose (55.5 MBq) tumor growth of NIS expressing HepG2 xenografts was significantly inhibited. In conclusion, tumor-specific iodide accumulation was induced in HCC cells by AFP promoter-directed NIS expression in vitro and in vivo, which was sufficiently high to allow a therapeutic effect of (131)I. This study demonstrates the potential of tumor-specific NIS gene therapy as an innovative treatment strategy for HCC.

Radiation and inhibition of angiogenesis by canstatin synergize to induce HIF-1alpha-mediated tumor apoptotic switch

Tumor radioresponsiveness depends on endothelial cell death, which leads in turn to tumor hypoxia. Radiation-induced hypoxia was recently shown to trigger tumor radioresistance by activating angiogenesis through hypoxia-inducible factor 1-regulated (HIF-1-regulated) cytokines. We show here that combining targeted radioiodide therapy with angiogenic inhibitors, such as canstatin, enhances direct tumor cell apoptosis, thereby overcoming radio-induced HIF-1-dependent tumor survival pathways in vitro and in vivo. We found that following dual therapy, HIF-1alpha increases the activity of the canstatin-induced alpha(v)beta(5) signaling tumor apoptotic pathway and concomitantly abrogates mitotic checkpoint and tetraploidy triggered by radiation. Apoptosis in conjunction with mitotic catastrophe leads to lethal tumor damage. We discovered that HIF-1 displays a radiosensitizing activity that is highly dependent on treatment modalities by regulating key apoptotic molecular pathways. Our findings therefore support a crucial role for angiogenesis inhibitors in shifting the fate of radiation-induced HIF-1alpha activity from hypoxia-induced tumor radioresistance to hypoxia-induced tumor apoptosis. This study provides a basis for developing new biology-based clinically relevant strategies to improve the efficacy of radiation oncology, using HIF-1 as an ally for cancer therapy.

Radioiodide imaging and radiovirotherapy of multiple myeloma using VSV(Delta51)-NIS, an attenuated vesicular stomatitis virus encoding the sodium iodide symporter gene

Multiple myeloma is a radiosensitive malignancy that is currently incurable. Here, we generated a novel recombinant vesicular stomatitis virus [VSV(Delta51)-NIS] that has a deletion of methionine 51 in the matrix protein and expresses the human sodium iodide symporter (NIS) gene. VSV(Delta51)-NIS showed specific oncolytic activity against myeloma cell lines and primary myeloma cells and was able to replicate to high titers in myeloma cells in vitro. Iodide uptake assays showed accumulation of radioactive iodide in VSV(Delta51)-NIS-infected myeloma cells that was specific to the function of the NIS transgene. In bg/nd/xid mice with established subcutaneous myeloma tumors, administration of VSV(Delta51)-NIS resulted in high intratumoral virus replication and tumor regression. VSV-associated neurotoxicity was not observed. Intratumoral spread of the infection was monitored noninvasively by serial gamma camera imaging of (123)I-iodide biodistribution. Dosimetry calculations based on these images pointed to the feasibility of combination radiovirotherapy with VSV(Delta51)-NIS plus (131)I. Immunocompetent mice with syngeneic 5TGM1 myeloma tumors (either subcutaneous or orthotopic) showed significant enhancements of tumor regression and survival when VSV(Delta51)-NIS was combined with (131)I. These results show that VSV(Delta51)-NIS is a safe oncolytic agent with significant therapeutic potential in multiple myeloma.

Experimental Study Enhancing the Chemosensitivity of Multiple Myeloma to Melphalan by Using a Tissue-Specific APE1-Silencing RNA Expression Vector

PURPOSE

Because of a developing resistance to chemotherapy agents, multiple myeloma (MM) has been an incurable disease until now. As a means to overcome MM tumor cell resistance and/or sensitize tumor cells to chemotherapeutic treatments currently used, we examined the role of human apurinic/apyrimidinic endonuclease 1 (APE1) in resistance and prognosis in patients with MM.

PATIENTS AND METHODS

Multiple myeloma cells were analyzed by using bone marrow specimens from 32 patients with MM and 10 normal volunteers.

RESULTS

The positive rate of APE1 protein expression was 65.6% in the bone marrow specimens of patients with MM with known clinical outcome. Positive rate of APE1 expression beyond grade 2 in the relapsed/refractory group was significantly higher than that in the untreated group. No positive results of grade > 2 were detected in bone marrow specimens from patients with noncancerous disease. It was also confirmed that the amount of APE1 protein in KM3 cells was positively correlated with the dose and action time of melphalan. Because APE1 was overexpressed in refractory/relapsed MM cells, siRNA-targeted technology was used to decrease APE1 levels in KM3 cells, with protein levels deceasing to 80%-90% within 24 hours and continuing to decease for 72 hours. The best dose and time of inhibiting expression of APE1 protein were 3 mug and 2 days long. A decrease in APE1 levels in siRNA-treated KM3 cells led to enhanced cell sensitization to melphalan.

CONCLUSION

The findings herein present prognostic and therapeutic implications for treating relapsed/refractory MM. The APE1-silencing RNA results demonstrate the feasibility of the therapeutic modulation of APE1 using a variety of molecules and approaches.

Efficacy of 99mTc pertechnetate and 131I radioisotope therapy in sodium/iodide symporter (NIS)-expressing neuroendocrine tumors in vivo

PURPOSE

There is growing interest in the human sodium/iodide symporter (NIS) gene both as a molecular imaging reporter gene and as a therapeutic gene. Here, we show the feasibility of radioisotope therapy of neuroendocrine tumors. As a separate application of NIS gene transfer, we image NIS-expressing tumors with pinhole SPECT in living subjects.

METHODS

Biodistribution studies and in vivo therapy experiments were performed in nude mice carrying stably NIS-expressing neuroendocrine tumor xenografts following i.v. injection of (131)I and (99m)Tc pertechnetate. To show the usefulness of NIS as an imaging reporter gene, (99m)Tc pertechnetate uptake was imaged in vivo using a clinical gamma camera in combination with a custom-made single pinhole collimator, followed by SPECT/small animal MRI data coregistration.

RESULTS

NIS-expressing neuroendocrine tumors strongly accumulated (131)I and (99m)Tc pertechnetate, as did thyroid, stomach, and salivary gland. The volume of NIS-expressing neuroendocrine tumors decreased significantly after therapeutic administration of (131)I or (99m)Tc pertechnetate, whereas control tumors continued to grow. NIS-mediated uptake of (99m)Tc pertechnetate could be imaged in vivo at high resolution with a clinical gamma camera equipped with a custom-made single pinhole collimator. High-resolution functional and morphologic information could be combined in a single three-dimensional data set by coregistration of SPECT and small animal MRI data. Lastly, we demonstrated a therapeutic effect of (99m)Tc pertechnetate on NIS-expressing neuroendocrine tumors in cell culture and, for the first time, in vivo, thought to be due to emitted Auger and conversion electrons.

CONCLUSIONS

NIS-expressing neuroendocrine tumors efficiently concentrate radioisotopes, allowing for in vivo high-resolution small animal SPECT imaging as well as rendering possible successful radioisotope therapy of neuroendocrine tumors.

Rat sodium iodide symporter allows using lower dose of 131I for cancer therapy

Efficient gene delivery is a critical obstacle for gene therapy that must be overcome. Until current limits of gene delivery technology are solved, identification of systems with bystander effects is highly desirable. As an anticancer agent, radioactive iodine (131)I has minimal toxicity. The physical characteristics of (131)I decay allow radiation penetration within a local area causing bystander killing of adjacent cells. Accumulation of (131)I mediated by the sodium iodide symporter (NIS) provides a highly effective treatment for well-differentiated thyroid carcinoma. Other types of cancer could also be treated by NIS-mediated concentration of lethal (131)I radiation in tumor cells. Our group and others previously reported that a significant antitumor effect in mice was achieved after adenoviral delivery of rat or human NIS gene following administration of 3 mCi of (131)I. We have also demonstrated 5-6-fold greater uptake of (125)I by rat NIS over human NIS in human cancer cells. Recently, we reported the capability of the rat NIS and (131)I to effectively induce growth arrest of relatively large tumors (approximately 800 mm(3)) in an animal model. In the present work tumor growth inhibition was achieved using adenoviral delivery of the rat NIS gene and 1 mCi of (131)I (one-third of the dose used in earlier reports). We also demonstrated that a higher concentration of (123)I was accumulated in the NIS-expressing tumors than in the thyroid 20 min after radioiodine administration. The highest intratumoral radioiodine concentration was observed along the needle track; however, the rat NIS-(131)I effectively induced growth arrest of tumor xenografts in mice through its radiological bystander effect. Importantly, the rat NIS allowed reducing the injected radioiodine dose by 70% with the same antitumor efficacy in pre-established tumors. These results suggest that the rat NIS gene may be advantageous compared to the human gene in its ability to enhance intratumoral (131)I uptake.

Non-invasive molecular imaging and reporter genes

Molecular-genetic imaging in living organisms has become a new field with the exceptional growth over the past 5 years. Modern imaging is based on three technologies: nuclear, magnetic resonance and optical imaging. Most current molecular-genetic imaging strategies are “indirect,” coupling a “reporter gene” with a complimentary “reporter probe.” The reporter transgene usually encodes for an enzyme, receptor or transporter that selectively interacts with a radiolabeled probe and results in accumulation of radioactivity in the transduced cell. In addition, reporter systems based on the expression of fluorescence or bioluminescence proteins are becoming more widely applied in small animal imaging. This review begins with a description of Positron Emission Tomography (PET)-based imaging genes and their complimentary radiolabeled probes that we think will be the first to enter clinical trials. Then we describe other imaging genes, mostly for optical imaging, which have been developed by investigators working with a variety of disease models in mice. Such optical reporters are unlikely to enter the clinic, at least not in the near-term. Reporter gene constructs can be driven by constitutive promoter elements and used to monitor gene therapy vectors and the efficacy of gene targeting and transduction, as well as to monitor adoptive cell-based therapies. Inducible promoters can be used as “sensors” to monitor endogenous cell processes, including specific intracellular molecular-genetic events and the activity of signaling pathways, by regulating the magnitude of reporter gene expression.

Hydrocortisone and purinergic signaling stimulate sodium/iodide symporter (NIS)-mediated iodide transport in breast cancer cells

The sodium/iodide symporter (NIS) mediates a remarkably effective targeted radioiodide therapy in thyroid cancer; this approach is an emerging candidate for treating other cancers that express NIS, whether endogenously or by exogenous gene transfer. Thus far, the only extrathyroidal malignancy known to express functional NIS endogenously is breast cancer. Therapeutic efficacy in thyroid cancer requires that radioiodide uptake be maximized in tumor cells by manipulating well-known regulatory factors of NIS expression in thyroid cells, such as TSH, which stimulates NIS expression via cAMP. Similarly, therapeutic efficacy in breast cancer will likely depend on manipulating NIS regulation in mammary cells, which differs from that in the thyroid. Human breast adenocarcinoma MCF-7 cells modestly express endogenous NIS when treated with all-trans-retinoic acid (tRa). We report here that hydrocortisone and ATP each markedly stimulates tRa-induced NIS protein expression and plasma membrane targeting in MCF-7 cells, leading to at least a 100% increase in iodide uptake. Surprisingly, the adenyl cyclase activator forskolin, which promotes NIS expression in thyroid cells, markedly decreases tRa-induced NIS protein expression in MCF-7 cells. Isobutylmethylxanthine increases tRa-induced NIS expression in MCF-7 cells, probably through a purinergic signaling system independent of isobutylmethylxanthine's action as a phosphodiesterase inhibitor. We also observed that neither iodide, which at high concentrations down-regulates NIS in the thyroid, nor cAMP has a significant effect on NIS expression in MCF-7 cells. Our findings may open new strategies for breast-selective pharmacological modulation of functional NIS expression, thus improving the feasibility of using radioiodide to effectively treat breast cancer.

Mathematical modeling of cancer radiovirotherapy

Cancer virotherapy represents a dynamical system that requires mathematical modeling for complete understanding of the outcomes. The combination of virotherapy with radiation (radiovirotherapy) has been recently shown to successfully eliminate tumors when virotherapy alone failed. However, it introduces a new level of complexity. We have developed a mathematical model, based on population dynamics, that captures the essential elements of radiovirotherapy. The existence of corresponding equilibrium points related to complete cure, partial cure, and therapy failure is proved and discussed. The parameters of the model were estimated by fitting to experimental data. By using simulations we analyzed the influence of parameters that describe the interaction between virus and tumor cell on the outcome of the therapy. Furthermore, we evaluated relevant therapeutic scenarios for radiovirotherapy, and offered elements for optimization.